Learn IPv4 classes, binary bitwise masks, Little Richard's 3 Rules, and Class C Sunny Subnetting Table
01 · LITTLE RICHARD'S 3 RULES OF THE SUBNET MASK
Little Richard's Rules of the Subnet Mask
3 Fundamental Rules Every Networking Student Must Know
RULE #1
It's NOT an IP address!
Never treat a subnet mask as an endpoint or device address. It is not assigned to a PC, server, printer, or router interface host IP.
RULE #2
It is a series of 1's followed by 0's!
In binary format, subnet masks are strictly contiguous 1-bits followed by 0-bits. You can NEVER mix or alternate 1s and 0s (e.g. 11111111.11111111.11111111.11000000).
RULE #3
It defines the Network & Host portions!
That is its ONLY job. The 1-bits lock down the Network ID portion of the address, and the 0-bits define the Host portion.
Subnet Mask Binary Rule Tester
Test your understanding of Rule #2: Enter a subnet mask in dotted-decimal notation to verify if it is a valid continuous binary mask!
02 · STANDARD IPv4 CLASSES & FORMULAS
Before Classless Inter-Domain Routing (CIDR), IPv4 addresses were split into five standard classes determined by their leading binary bits:
Class
First Octet Range
Leading Bits
Default Mask
CIDR
Usable Hosts / Net
Class A
1.0.0.0 – 126.255.255.255
0...
255.0.0.0
/8
16,777,214 hosts (224 - 2)
Class B
128.0.0.0 – 191.255.255.255
10...
255.255.0.0
/16
65,534 hosts (216 - 2)
Class C
192.0.0.0 – 223.255.255.255
110...
255.255.255.0
/24
254 hosts (28 - 2)
Class D
224.0.0.0 – 239.255.255.255
1110...
Multicast
N/A
Reserved for Multicast Groups
Class E
240.0.0.0 – 255.255.255.255
1111...
Experimental
N/A
Reserved for Research & R&D
Note:127.0.0.0/8 is reserved for Loopback testing (e.g. 127.0.0.1) and is not assigned as a standard host range.
THE 3 GOLDEN SUBNETTING FORMULAS
1. Number of Subnets Created:Subnets = 2^b(where b = borrowed network bits)2. Total Block Size (Addresses):Block Size = 2^h(where h = remaining host bits)3. Usable Hosts per Subnet:Usable = (2^h) − 2(Subtract 2 for Network ID & Broadcast ID)
03 · BINARY BITWISE AND VISUALIZER
See how a computer uses Little Richard's Rule #3 by performing a bitwise AND operation (1 AND 1 = 1) to isolate the Network ID!
04 · SUNNY SUBNETTING TABLE (CLASS C CHEAT SHEET)
Not confident with math yet? Use the Sunny Subnetting Table! Click on any CIDR prefix column below to immediately reveal the Subnets, Block Size, Usable Hosts, and Subnet Mask octet without doing any calculations!
Sunny Subnetting Table
1
2
4
8
16
32
64
128
256
Subnet (Count)
1
2
4
8
16
32
64
128
256
Host (Block Size)
256
128
64
32
16
8
4
2
1
Subnet Mask (CIDR)
/24
/25
/26
/27
/28
/29
/30
/31
/32
05 · INTERACTIVE SUBNETTING SCENARIOS
06 · GEMINI NOTEBOOK & NOTEBOOKLM SOURCE CONTENT
Copy the formatted content below directly into Gemini Notebook or NotebookLM to generate visual study guides, flashcards, or a 2-person podcast audio overview!
# Master IPv4 Subnetting & Little Richard's 3 Rules
> Gemini Notebook & NotebookLM Source Material
## Little Richard's 3 Rules of the Subnet Mask
1. IT IS NOT AN IP ADDRESS!
2. IT IS ALWAYS A SERIES OF 1's FOLLOWED BY A SERIES OF 0's IN BINARY!
3. IT DEFINES THE NETWORK PORTION AND HOST PORTION OF AN ADDRESS!
## Sunny Subnetting Table (Class C)
Subnet: 1 | 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256
Host: 256 | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1
Subnet Mask: /24 | /25 | /26| /27| /28| /29| /30| /31 | /32
## Standard IPv4 Classes
Class A: 1.0.0.0 – 126.255.255.255 (Default /8)
Class B: 128.0.0.0 – 191.255.255.255 (Default /16)
Class C: 192.0.0.0 – 223.255.255.255 (Default /24)
## Core Formulas
- Subnets Created = 2^b (where b = borrowed bits)
- Total Block Size = 2^h (where h = remaining host bits)
- Usable Hosts = (2^h) - 2 (Subtract Network ID and Broadcast ID)